1. Field of the Invention
The present invention relates to a suspension device for a bicycle.
2. Description of the Background Art
Conventionally, in an off-road bicycle, there has been employed "a suspension device which comprises a pair of left and right slide tubes fixed to a steering bracket rotatably supported at the front end portion of a frame of the bicycle, and a pair of left and right cylindrical fork legs slidably engaged with the slide tubes and holding a front wheel, fluid chambers and gas chambers being defined within internal spaces respectively extending between the slide tubes and the fork legs, and damping force generating devices disposed within the fluid chambers between the slide tubes and the fork legs", as disclosed in Japanese Unexamined Patent Publication No. 2-231289.
With such a suspension device, upon relative movement between the sliding tubes and fork legs by expansion and compression due to undulation of the road surface, road shock can be absorbed by the action of a pneumatic spring generated as a reaction force of gas pressure in the gas chambers and by damping function provided by the damping force generating device for the working fluid in the fluid chamber.
In the above-mentioned prior art, a gas valve acting as an enclosed gas pressure adjusting means is provided in a top end cap of the slide tube so as to attain a pneumatic spring force of the gas spring necessary for certainly provide desired level of riding comfort depending upon the taste and weight of the rider.
However, in the prior art, there have been encountered problems 1 and 2 set out below.
1 When adjusting the enclosed gas pressure, a gas supply device has to be connected to the gas valve for increasing the pressure and gas discharging operation must be used a gas discharging tool. The need to use a gas supply device and a gas discharging tool to make adjustment of the enclosed gas pressure during use of the bicycle is made very difficult. PA1 2 The need to provide a gas valve as the enclosed gas pressure adjusting means in the cap of slide tube creates a rise in cost. Furthermore, if an operation member of an adjuster extending in the axial direction of the slide tube is used as a damping force adjusting means of the above-mentioned damping force generating device, it would be provided in the cap of the slide tube, and the operation member for the adjuster would need to be provided in the cap, to which the air valve has to be provided, all of which would make the configuration of the cap extremely complicated. PA1 a pair of left and right slide tubes fixed to a steering bracket which is, in turn, rotatably supported at the front portion of the bicycle; PA1 a pair of left and right fork legs coupled with the slide tube in slidable fashion and holding a front wheel; PA1 fluid chambers and gas chambers extending over both of the slide tube and the fork leg; PA1 damping force generating device provided within the fluid chamber between the slide tube and the fork leg; PA1 the suspension device further comprising: